Ceramics may generally be defined as products manufactured by the action of heat on earthy raw materials in which silicon with its oxide and silicates occupy a predominant position. Various types of products are made from ceramics including structural clay products (such as brick, tile, terra cotta and glazed architectural brick); whitewares (such as dinnerware, chemical and electrical porcelain, sanitary ware and floor tile); glass products of all types; porcelain enamels; refractories; Portland cement, lime, plaster and gypsum products; abrasive materials such as fused alumina, silicon carbide and related products; and, aluminum silicate fibres.
Clay based ceramic products have become a staple in many areas of industry including the construction industry. In particular, structural clay products are used extensively in the construction of buildings.
Accordingly, one disadvantage of structural clay products is that an extensive amount of time is required to produce a single product. Further, large amounts of energy must be utilized during the baking process in the kiln. Typically, in order for a manufacturing plant to be economically efficient, kilns having a capacity to simultaneously bake a large quantity of bricks are required. In addition, manufacturing plants tend to be located near the source of the clay, thus increasing the cost of transporting the bricks to the construction site where they will be used.
More recently, silicate based material has been utilized to produce bricks. For example, calcium silicate bricks may be prepared by grinding lime together with sand to produce a lime-silica bonding adhesive, mixing this adhesive with sand, pressing the mixture of sand and bonding adhesive into a mold and baking the mixture in an autoclave. Calcium silicate bricks may be utilized in place of more conventional clay bricks in the construction industry.
One disadvantage with calcium silicate bricks is the amount of time required to produce a single brick. In addition, a large amount of processing equipment and power input is required to produce calcium silicate bricks.
Binding compositions have also been prepared by the wet grinding of sand in an alkaline medium. According to the method disclosed in U.S.S.R. Author's Priority Certificate No. 992487, sand is ground in a ball mill in an alkaline medium (pH 9.0-10.5) to produce a silica based binding composition. The feedstock is divided into three portions. The first portion, which comprises 50% of the feedstock of sand, is milled for 6 hours. In the presence of a waterglass having a pH of 10.5. The second portion, which comprises 25% of the initial feedstock, is then combined with the milled feedstock and the mixture is milled for 7 hours. The third portion, which comprises 25% of the initial feedstock, is added to this milled product and this mixture is then milled for an additional 12 hours. One disadvantage of this method is that each batch requires 24 hours of milling time. This reduces the potential throughput of the process. In addition, the lengthy grinding time increase the wear of the components of the ball mill and substantially decrease the lifetime of the ball mill. In addition, the product produced by this method may not have sufficient compressive strength for use in some applications.